WO2010101409A2 - Method and apparatus for reporting channel state in multi-carrier system - Google Patents

Abstract

A method and an apparatus for reporting a channel state in a multi-carrier system are provided. User equipment receives an uplink grant including an uplink resource allocation and a channel quality indicator (CQI) request via one downlink carrier from among a plurality of downlink carriers. The user equipment reports CQIs for the plurality of downlink carriers via a plurality of subframes in accordance with the CQI request.

Description

Method and device for reporting channel status in multi-carrier system

The present invention relates to wireless communication, and more particularly, to a method and apparatus for reporting channel status in a wireless communication system supporting multiple carriers.

Wireless communication systems are widely deployed to provide various kinds of communication services such as voice and data. In general, a wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of multiple access systems include code division multiple access (CDMA) systems, frequency division multiple access (FDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single carrier frequency (SC-FDMA). division multiple access) system.

In a typical wireless communication system, even though the bandwidth between uplink and downlink is set differently, only one carrier is considered. Carrier is defined by the center frequency (band frequency) and bandwidth. Multi-carrier system is to use a plurality of carriers having a bandwidth less than the total bandwidth.

Long term evolution (LTE), based on the 3rd Generation Partnership Project (3GPP) Technical Specification (TS) Release 8, is a leading next-generation mobile communication standard.

As disclosed in 3GPP TS 36.211 V8.5.0 (2008-12) "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)", the physical channel in LTE is a physical channel, PDSCH (Physical Downlink Shared) Channel (Physical Uplink Shared Channel) and PUSCH (Physical Downlink Control Channel), PCFICH (Physical Control Format Indicator Channel), PHICH (Physical Hybrid-ARQ Indicator Channel) and PUCCH (Physical Uplink Control Channel) Can be.

The 3GPP LTE system supports only one bandwidth (ie, one carrier) of {1.4, 3, 5, 10, 15, 20} MHz. The multi-carrier system uses two carriers having a 20 MHz bandwidth or three carriers having a 20 MHz bandwidth, a 15 MHz bandwidth, and a 5 MHz bandwidth to support a full bandwidth of 40 MHz.

The multi-carrier system can support backward compatibility with the existing system, and also has an advantage of significantly increasing the data rate through the multi-carrier.

In a single carrier system, a control channel and a data channel are designed based on a single carrier. However, if the channel structure of a single carrier system is used as it is in a multi-carrier system, it may be inefficient.

Channel Quality Indicator (CQI) indicates a channel condition. The CQI is used by the base station to schedule the terminal in the cell. In a multi-carrier system, CQI for each carrier is required for scheduling for each carrier. However, if CQIs are reported for all carriers, radio resources may be used inefficiently.

There is a need for a method and apparatus for reporting CQI in a multi-carrier system.

An object of the present invention is to provide a method and apparatus for supporting multiple carriers.

An object of the present invention is to provide a method and apparatus for monitoring a control channel in a multi-carrier system.

In one aspect, a channel state reporting method in a multi-carrier system is provided. In the method, the terminal receives an uplink grant including an uplink resource allocation and a channel quality indicator (CQI) request through one downlink carrier among a plurality of downlink carriers, and the terminal according to the CQI request Reporting CQI for a plurality of downlink carriers over a plurality of subframes.

The CQI for each of the plurality of downlink carriers may be reported in each of the plurality of subframes.

The plurality of subframes may be spaced apart at offset intervals.

In another aspect, a terminal for reporting a channel state in a multi-carrier system includes an RF unit for transmitting and receiving a radio signal, and a processor connected to the RF unit, the processor is uplink resource allocation and CQI (Channel Quality) Indicator) receiving an uplink grant including a request through one downlink carrier among a plurality of downlink carriers, and reporting CQIs for the plurality of downlink carriers over a plurality of subframes according to the CQI request. .

While maintaining the structure of the existing 3GPP LTE, it is possible to report the channel state for a plurality of carriers. It is possible to report the channel state for a plurality of carriers without additional uplink grant.

1 shows a wireless communication system.

2 shows a structure of a radio frame in 3GPP LTE.

3 shows an example of an uplink subframe in 3GPP LTE.

4 is a flowchart illustrating a method of reporting aperiodic CQI in 3GPP LTE.

5 shows CQI transmission on a PUSCH.

6 shows an example of operating a multi-carrier.

7 shows an example of operation in a multi-carrier.

8 is a flowchart illustrating a CQI reporting method according to an embodiment of the present invention.

9 shows an example of a joint coded PDCCH.

10 is a block diagram illustrating a wireless communication system in which an embodiment of the present invention is implemented.

1 shows a wireless communication system. The wireless communication system 10 includes at least one base station (BS) 11. Each base station 11 provides a communication service for a particular geographic area (generally called a cell) 15a, 15b, 15c. The cell can in turn be divided into a number of regions (called sectors).

The user equipment (UE) 12 may be fixed or mobile, and may include a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, and a PDA. (personal digital assistant), wireless modem (wireless modem), a handheld device (handheld device) may be called other terms.

The base station 11 generally refers to a fixed station communicating with the terminal 12, and may be referred to as other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, and the like. have.

Hereinafter, downlink (DL) means communication from the base station to the terminal, and uplink (UL) means communication from the terminal to the base station. In downlink, a transmitter may be part of a base station, and a receiver may be part of a terminal. In uplink, a transmitter may be part of a terminal, and a receiver may be part of a base station.

2 shows a structure of a radio frame in 3GPP LTE. It may be referred to section 6 of 3GPP TS 36.211 V8.5.0 (2008-12) "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)". A radio frame consists of 10 subframes indexed from 0 to 9, and one subframe consists of two slots. The time it takes for one subframe to be transmitted is called a transmission time interval (TTI). For example, one subframe may have a length of 1 ms and one slot may have a length of 0.5 ms.

One slot may include a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain. Since OFDM symbols use orthogonal frequency division multiple access (OFDMA) in downlink, the OFDM symbols are only intended to represent one symbol period in the time domain, and the limitation on the multiple access scheme or name is not limited. no. For example, the OFDM symbol may be called another name such as a single carrier frequency division multiple access (SC-FDMA) symbol, a symbol period, and the like.

One slot includes 7 OFDM symbols as an example, but the number of OFDM symbols included in one slot may vary according to the length of the Cyclic Prefix (CP). According to 3GPP TS 36.211 V8.5.0 (2008-12), one subframe includes 7 OFDM symbols in a normal CP and one subframe includes 6 OFDM symbols in an extended CP.

A resource block (RB) is a resource allocation unit and includes a plurality of subcarriers in one slot. For example, if one slot includes 7 OFDM symbols in the time domain and the resource block includes 12 subcarriers in the frequency domain, one resource block may include 7 × 12 resource elements (REs). Can be.

The primary synchronization signal (PSS) is transmitted in the last OFDM symbol of the first slot (the first slot of the first subframe (index 0 subframe)) and the 11th slot (the first slot of the sixth subframe (index 5 subframe)). do. PSS is used to obtain OFDM symbol synchronization or slot synchronization and is associated with a physical cell identity. Primary Synchronization Code (PSC) is a sequence used for PSS, and 3GPP LTE has three PSCs. One of three PSCs is transmitted to the PSS according to the cell ID. The same PSC is used for each of the last OFDM symbols of the first slot and the eleventh slot.

The secondary synchronization signal (SSS) includes a first SSS and a second SSS. The first SSS and the second SSS are transmitted in an OFDM symbol adjacent to the OFDM symbol in which the PSS is transmitted. SSS is used to obtain frame synchronization. The SSS is used to obtain a cell ID along with the PSS. The first SSS and the second SSS use different Secondary Synchronization Codes (SSCs). When the first SSS and the second SSS each include 31 subcarriers, each of two SSC sequences having a length of 31 is used for the first SSS and the second SSS.

The Physical Broadcast Channel (PBCH) is transmitted in the preceding four OFDM symbols of the second slot of the first subframe. The PBCH carries system information necessary for the terminal to communicate with the base station, and the system information transmitted through the PBCH is called a master information block (MIB). In comparison, system information transmitted through a physical downlink control channel (PDCCH) is called a system information block (SIB).

As disclosed in 3GPP TS 36.211 V8.5.0 (2008-12), LTE uses a physical downlink shared channel (PDSCH), a physical downlink shared channel (PUSCH), a physical downlink shared channel (PUSCH), and a physical downlink control channel (PDCCH), a control channel. And PUCCH (Physical Uplink Control Channel). In addition, a downlink control channel includes a Physical Control Format Indicator Channel (PCFICH) and a Physical Hybrid-ARQ Indicator Channel (PHICH).

Control information transmitted through the PDCCH is called downlink control information (DCI). The DCI may include resource allocation of the PDSCH (also called downlink grant), resource allocation of the PUSCH (also called uplink grant), a set of transmit power control commands for individual UEs in any UE group, and / or VoIP (Voice). over Internet Protocol).

3 shows an example of an uplink subframe in 3GPP LTE. The uplink subframe may be divided into a control region to which a physical uplink control channel (PUCCH) carrying uplink control information is allocated and a data region to which a physical uplink shared channel (PUSCH) carrying uplink data is allocated.

PUCCH for one UE is allocated to a resource block pair in a subframe. Resource blocks belonging to a resource block pair occupy different subcarriers in each of a first slot and a second slot. m is a location index indicating a logical frequency domain location of a resource block pair allocated to a PUCCH in a subframe. It is shown that a resource block having the same m value occupies different subcarriers in two slots.

4 is a flowchart illustrating a method of reporting aperiodic CQI in 3GPP LTE. Aperiodic CQI is a CQI reported by a UE according to a request of a base station, and a periodic CQI is a CQI reported in a predetermined period without a request of a base station.

The base station sends a CQI request (request) on the PDCCH to the terminal (S110). As disclosed in section 5.3.3.1.1 of 3GPP TS 36.212 V8.5.0 (2008-12), the CQI request is a 1-bit field included in DCI format 0, which is an uplink grant for PUSCH scheduling. Table 1 below is an example of fields included in DCI format 0.

Table 1

Field name	Explanation
Uplink Resource Allocation	Resource Allocation for PUSCH
CQI request	Triggering of CQI Report Requests

If the bit value of the CQI request is set to '1' in the nth subframe, the UE reports the CQI on the PUSCH in the n + kth subframe (S120). K = 4 in the frequency division duplex (FDD). The PUSCH may be configured through an uplink grant including a CQI request. That is, the terminal receives the uplink resource allocation and the CQI request, and multiplexes the CQI to the uplink data by using the uplink resource allocation.

5 shows CQI transmission on a PUSCH. 'RS' assigned to the center OFDM symbol of the slot means a reference signal. The CQI is time-first mapped at the top of the data area. An 'ACK' and an RI (rank indicator), which are ACK / NACK signals for HARQ, may also be transmitted on the PUSCH.

As disclosed in section 7.2.1 of 3GPP TS 36.213 V8.5.0 (2008-12), one of the six modes in the following table is set to the reporting mode for CQI reporting. The reporting mode is set by the RRC message.

TABLE 2

		PMI Feedback Type
		No PMI	Single PMI	Multiple PMI
CQI Feedback Type	Wideband CQI			Mode 1-2
	Subband CQI (UE selected)	Mode 2-0		Mode 2-2
	Subband Higher Layer configured (CQI)	Mode 3-0	Mode 3-1

The wideband CQI refers to the CQI for the entire band, and the subband CQI refers to the CQI for some bands of the entire band.

CQI reporting in 3GPP LTE is based on a single carrier system in which a downlink carrier on which a CQI request is transmitted and an uplink carrier on which a CQI is transmitted are mapped 1: 1.

In the following, CQI is an indicator indicating channel status. The CQI may be expressed as an index of an MCS (modulation and coding) table, but may be expressed in various ways such as interference level or signal strength. In addition, the CQI may further include a precoding matrix indicator (PMI) indicating an index of the precoding matrix and / or a rank indicator (RI) indicating a rank.

Now, a multi-carrier system will be described.

The 3GPP LTE system supports a case where the downlink bandwidth and the uplink bandwidth are set differently, but this assumes one component carrier (CC). This means that 3GPP LTE is supported only when the bandwidth of the downlink and the bandwidth of the uplink are the same or different in a situation in which one component carrier is defined for the downlink and the uplink, respectively. For example, the 3GPP LTE system supports up to 20MHz and may have different uplink and downlink bandwidths, but only one component carrier is supported for uplink and downlink.

Spectrum aggregation (or bandwidth aggregation, also called carrier aggregation) is to support a plurality of component carriers. Spectral aggregation is introduced to support increased throughput, to prevent cost increases due to the introduction of wideband radio frequency (RF) devices, and to ensure compatibility with existing systems. For example, if five component carriers are allocated as granularity in a carrier unit having a 20 MHz bandwidth, a bandwidth of up to 100 MHz may be supported.

Spectral aggregation can be divided into contiguous spectral aggregation where aggregation is between successive carriers in the frequency domain and non-contiguous spectral aggregation where aggregation is between discontinuous carriers. The number of carriers aggregated between the downlink and the uplink may be set differently. The case where the number of downlink carriers and the number of uplink carriers are the same is called symmetric aggregation, and when the number is different, it is called asymmetric aggregation.

The size (ie, bandwidth) of component carriers may be different from each other. For example, assuming that five component carriers are used for the configuration of the 70 MHz band, a 5 MHz carrier (carrier # 0) + 20 MHz carrier (carrier # 1) + 20 MHz carrier (carrier # 2) + 20 MHz carrier (carrier # 3 ) + 5MHz carrier (carrier # 4) may be configured.

Hereinafter, a multiple carrier system refers to a system supporting multiple carriers based on spectral aggregation. Adjacent spectral and / or non-adjacent spectral aggregation may be used in a multi-carrier system, and either symmetric or asymmetric aggregation may be used.

6 shows an example of operating a multi-carrier. There are four DL CCs (DL CC # 1, DL CC # 2, DL CC # 3, DL CC # 4) and three UL CCs (UL CC # 1, UL CC # 2, UL CC # 3), but CC There is no limit to the number of.

Of the four DL CCs, DL CC # 1 and DL CC # 2 are activated, and these are called activated carriers, and DL CC # 3 and DL CC # 4 are deactivated, and these are called deactivated carriers. In addition, of the three UL CCs, UL CC # 1 and UL CC # 2 are active carrier waves, and UL CC # 3 is an inactive carrier wave.

An active carrier is a carrier that can transmit or receive control information or data packets. Inactive carriers are not capable of transmitting or receiving data packets, but at least operations such as signal measurement are possible.

The active carrier and the inactive carrier are not fixed, but each CC may be deactivated or activated by negotiation with the base station and the terminal. An inactive carrier is also called a candidate carrier in that it can be activated.

At least one of the active carriers may be set as a reference carrier. The reference carrier is called an anchor carrier or a primary carrier. An active carrier other than a reference carrier is called a secondary carrier. The reference carrier is a carrier on which control information is transmitted on a downlink control channel (eg, PDCCH) or common control information for multiple carriers.

A mobility management or carrier activation / deactivation message may be transmitted through the reference carrier.

The reference carrier may be defined for uplink as well as downlink. The uplink reference carrier may be used to transmit at least one of uplink control information (UCI), HARQ ACK / NACK signal, aperiodic CQI, and periodic CQI. In addition, the uplink reference carrier may be used to perform handover or to perform initial access such as transmission of a random access preamble.

7 shows an example of operation in a multi-carrier.

The base station sends the first uplink grant to the terminal on the first PDCCH 210 of the DL CC. The first uplink grant includes information on resource allocation of the first PUSCH 215 of the UL CC # 1.

The base station sends a second uplink grant to the terminal on the second PDCCH 220 of the DL CC. The second uplink grant includes information on resource allocation of the first PUSCH 225 of the UL CC # 2.

The uplink grant may include a carrier indicator field (CIF) for indicating which UL CC is an uplink grant. Or, the UE can implicitly know the UL CC through the resources of the PDCCH through which the uplink grant is transmitted.

8 is a flowchart illustrating a CQI reporting method according to an embodiment of the present invention.

The base station sends a CQI request to the terminal (S210). The CQI request may be sent on the PDCCH as part of the DCI, but may be sent on an RRC message. Uplink resource allocation can be transmitted along with the CQI request.

The UE sends the first CQI for the DL CC # 1 on the PUSCH (S220). If the CQI request is received in the nth subframe, the first CQI may be sent in the n + k1th subframe. k1> 0, and k1 = 4 is shown here as an example.

The terminal then sends a second CQI for DL CC # 2 (S230). If the first CQI is sent in the n + k1 th subframe, the second CQI may be sent in the n + k1 + k2 subframe. k2> 0, and k2 = 4 is shown here as an example.

Triggering a CQI request while sending an uplink grant for each CC may cause waste of transmitting an uplink grant for a CQI report request even to a CC for which an uplink grant is not required. Therefore, when one CQI request is triggered, the CQI for another CC can be transmitted over a plurality of subframes without a separate uplink grant.

If the DL CC is an inactive carrier, it may not be able to send an uplink grant and thus may not receive a CQI at all. Accordingly, overhead due to unnecessary transmission of an uplink grant is prevented, and CQIs for a plurality of DL CCs can be transmitted through one uplink grant for scheduling (activation / deactivation of a carrier) of multiple carriers.

The offset (or period) k1 and / or k2 of the subframe in which the CQI is transmitted may be specified in advance, but the base station may inform the UE through an RRC message or a DCI on the PDCCH.

The CQI request to the UE may be triggered independently for each CC. Alternatively, one CQI request may be triggered for a plurality of CCs. The UE may receive an uplink grant including a CQI request through one or more DL CCs.

Here, although the CQI is transmitted through two subframes (n + k1th subframe and n + k2th subframe), the number of subframes is not limited. The CQI may be transmitted through P subframes or multiple subframes of P. The number P or the period of the subframe in which the CQI is reported may be specified in advance, but the base station may inform the UE through the RRC message or the DCI on the PDCCH. Each subframe may fall at a constant offset interval or may be spaced at different offset intervals.

Here, CQIs for one DL CC are transmitted in one subframe, but CQIs for a plurality of DL CCs may be transmitted. For example, the first CQI of the n + k1 subframe includes the CQIs for DL CC # 1 and DL CC # 3, and the second CQI of the n + k1 + k2 subframe is DL CC # 2 and DL It includes the CQI for CC # 4.

The order of DL CCs for which CQI is reported may be specified in advance, or the base station may send the order of DL CCs for reporting CQI to the UE. For example, the UE may transmit CQI for a plurality of DL CCs based on the DL CCs on which the CQI request is transmitted. Alternatively, the terminal may transmit the CQI in a predetermined report order regardless of the DL CC through which the CQI request is transmitted.

The CQI reporting mode may be the same for each CC or may be different for each CC. For example, DL CC # 1 is an active carrier for performing dynamic scheduling to the UE for each subband, and DL CC # 2 is an inactive carrier. The subband CQI is reported for the DL CC # 1, and the wideband CQI is reported for the DL CC # 2.

The base station may set the CQI reporting mode for each CC with the CQI request or through higher layer signaling.

The terminal may override the CQI reporting mode set by the base station. For example, if a reporting mode is configured to report subband CQI for DL CC # 2, but the DL CC # 2 is currently deactivated, the UE reports wideband CQI.

As in the conventional 3GPP LTE, the CQI request may be a field having 1 bit and triggering a CQI report. When the CQI request is received, the UE reports the CQI for the active carrier and / or inactive carrier. At this time, since there is only one uplink grant, it may be ambiguous which DL CC to report a CQI.

The DL CC for which the CQI is reported may be determined in various ways as follows.

In a first embodiment, the CQI is reported for the DL CC on which an uplink grant is transmitted. Let this be the reference DL CC. At this time, there is a linked UL CC linked with the reference DL CC. The linked UL CC is a UL CC through which a PUSCH is transmitted using the uplink grant. There may be a plurality of DL CCs linked with the linked UL CCs. The terminal reports CQIs for the plurality of DL CCs.

For example, suppose there are DL CC # 1, DL CC # 2, DL CC # 3, DL CC # 4, DL CC # 5, UL CC # 1, and UL CC # 2. In addition, it is assumed that UL CC # 1 is linked with DL CC # 1, DL CC # 2, and DL CC # 3, and UL CC # 2 is linked with DL CC # 4 and DL CC # 5. Here, 'link' means that uplink grant received through DL CC # 1, DL CC # 2, or DL CC # 3 is used by the linked UL CC # 1. If the uplink grant including the CQI request is received through the DL CC # 1, the UE transmits the CQI for the DL CC # 2 and the DL CC # 3 as well as the DL CC # 1.

The reporting of the CQI may be performed according to the order of the physical / logical index of the DL CC. For example, in the above example, the CQI for DL CC # 1 becomes the first CQI of the n + k1 th subframe, the CQI for DL CC # 2 becomes the second CQI of the n + k1 + k2 subframe, and DL The CQI for CC # 3 becomes the third CQI of the n + k1 + k2 + k3 subframes.

In a second embodiment, the base station may inform the terminal of the report list for the DL CC to report the CQI. The report list may be transmitted through part of system information or higher layer signaling such as an RRC message.

In a third embodiment, the CQI request may include information on the DL CC to report the CQI. For example, the uplink grant may be configured as shown in Table 3 below.

TABLE 3

Field name	Explanation
Uplink Resource Allocation	Resource Allocation for PUSCH
CQI request index 1	Index of the first DL CC for which CQI is to be reported
CQI request index 2	Index of the second DL CC for which CQI is to be reported

The index of the DL CC for which the CQI is to be reported may be a physical index or may be a logical index. CQI index 2 may be a value relative to CQI index 1.

Alternatively, the CQI request may include a bitmap of DL CCs to report the CQI. For example, the uplink grant may be configured as shown in Table 4 below.

Table 4

Field name	Explanation
Uplink Resource Allocation	Resource Allocation for PUSCH
CQI request	1-bit field that triggers CQI reporting
CQI reporting bitmap	Bitmap indicating the DL CC whose CQI is to be reported

The UL CC through which the PUSCH for the aperiodic CQI is transmitted may be a UL CC linked with the DL CC through which the uplink grant is transmitted. Alternatively, the UL CC in which the PUSCH for the aperiodic CQI is transmitted may be a single UL reference carrier or a UL CC allocated separately by the base station for CQI transmission to the UE.

If the UL CC used for transmission of the PUSCH for aperiodic CQI is a UL reference carrier, this reference carrier may be a single reference carrier file configured UE-specifically. In addition, this reference carrier may be the same as the carrier used for transmission of the HARQ ACK / NACK signal on the PUCCH.

9 shows an example of a joint coded PDCCH. Joint coding means that the DCI on the PDCCH includes a plurality of uplink grants for a plurality of carriers. In comparison, the transmission of one uplink grant on the PDCCH as shown in FIG. 7 is referred to as separate coding.

The base station is configured to terminal a first uplink grant for the first PUSCH 515 of UL CC # 1 and a second uplink grant for the second PUSCH 518 of UL CC # 2 on the PDCCH 510 of the DL CC. Send to

Upon receiving the CQI request included in the first uplink grant and / or the second uplink grant, the UE transmits CQIs for a plurality of DL CCs. CQI for a plurality of DL CCs may be transmitted over a plurality of uplink subframes as described in the above-described embodiment of FIG. 8.

The CQI may transmit the CQI on P subframes or multiple subframes of P. The number or period of subframes in which the CQI is reported may be specified in advance, but the base station may inform the UE through an RRC message or a DCI on the PDCCH.

CQI for one DL CC or CQI for a plurality of DL CCs may be transmitted through one PUSCH.

The order of DL CCs for which CQI is reported may be specified in advance, or the base station may send the order of DL CCs for reporting CQI to the UE. For example, the UE may transmit CQI for a plurality of DL CCs based on the DL CCs on which the CQI request is transmitted. Alternatively, the terminal may transmit the CQI in a predetermined report order regardless of the DL CC through which the CQI request is transmitted.

The CQI reporting mode may be the same for each CC or may be different for each CC. For example, DL CC # 1 is an active carrier for performing dynamic scheduling to the UE for each subband, and DL CC # 2 is an inactive carrier. The subband CQI is reported for the DL CC # 1, and the wideband CQI is reported for the DL CC # 2.

The base station may set the CQI reporting mode for each CC with the CQI request or through higher layer signaling.

The terminal may override the CQI reporting mode set by the base station. For example, if a base station sets a reporting mode to report a subband CQI for DL CC # 2, but the DL CC # 2 is currently deactivated, the terminal reports a wideband CQI.

Even if a plurality of uplink grants are transmitted on the PDCCH 510, only a 1-bit CQI request may be transmitted. In this case, the PDCCH 510 may report CQIs for a plurality of DL CCs jointly coded.

Even if there are a plurality of uplink grants, if the CQI request is 1 bit, it may be ambiguous to which DL CC to report the CQI. The DL CC in which the CQI is reported may be various ways as follows to determine the DL CC.

In a first embodiment, CQI is reported for one or a plurality of DL CCs on which a plurality of uplink grants are transmitted. In addition, if there is a linked UL CC linked with a plurality of DL CCs, it may be reported as a CQI for another DL CC linked to the linked UL CC. The reporting of the CQI may be performed according to the order of the physical / logical index of the DL CC.

In a second embodiment, the base station may inform the terminal of the report list for the DL CC to report the CQI. The report list may be transmitted through part of system information or higher layer signaling such as an RRC message.

In a third embodiment, the CQI request may include information on the DL CC to report the CQI. For example, in addition to a plurality of uplink grants on the PDCCH, the index or bitmap of the DL CC for which the CQI is to be reported may be transmitted.

In a multi-carrier system, the base station can evaluate the channel state in various ways, and thus the reporting mode of the CQI can be changed. For example, the CQI for scheduling in the carrier is obtained from the measurement result in the frequency / time domain within the carrier. CQI for scheduling between a plurality of carriers is obtained from the measurement results for each carrier. CQI for intercell scheduling is obtained from measurement results for a plurality of cells.

As a reporting mode, at least one of the six modes disclosed in 3GPP TS 36.213 V8.5.0 (2008-12) described above may be used, but a new reporting mode may be defined.

The reporting mode for reporting the CQI for scheduling in the carrier is set to include the best-M selection information for utilizing the subband CQI and frequency selectivity.

Since the reporting mode for reporting CQI for scheduling between a plurality of carriers is for carrier selective scheduling, the minimum information indicating the channel state of each carrier, for example, wideband CQI, wideband PMI, and / or wideband It may be set to include an RI. The CQI for scheduling between a plurality of carriers may be reported aperiodically, but may be reported periodically. In periodic reporting, since scheduling between a plurality of carriers is not frequently performed, a relatively long reporting period may be set. The period may be predefined or delivered in higher layer signaling. When the periodic CQI is transmitted, PUSCH may be used, and PUCCH may be used if there are available resources.

The reporting mode for CQI for intercell scheduling is set to include measurement results for neighbor cells in order to perform an operation such as CoMP (Coordinated Multipoint Transmission). The reporting mode may include a signal strength of a neighbor cell, a measurement result according to a specific criterion, and / or information related to propagation delay of the signal of the neighbor cell. The CQI for intercell scheduling may be reported aperiodically, but may be reported periodically. In periodic reporting, since scheduling between a plurality of carriers is not frequently performed, a relatively long reporting period may be set. The period may be predefined or delivered in higher layer signaling. When the periodic CQI is transmitted, PUSCH may be used, and PUCCH may be used if there are available resources.

In a multi-carrier system, a reporting mode for CQI is set through an RRC message, and CQI reporting can be performed by triggering a CQI request through a 1-bit field of PDCCH. Alternatively, the reporting mode may be dynamically set on the PDCCH.

The reporting mode may be set implicitly according to the DCI format of the PDCCH. For example, if the DCI format is related to CoMP, it is set to a reporting mode for intercell scheduling. If the DCI format is associated with multiple carriers, it is set to a reporting mode for scheduling between a plurality of carriers.

Now, the content included in the CQI is described.

In 3GPP LTE, wideband CQI and subband CQI are used as CQI. However, new CQI needs to be defined to support multiple carriers or CoMP.

When reporting CQI for multiple carriers, the CQI may include at least one of the following.

(1) Multiple carrier wideband CQI (Multiple Carrier Wideband CQI): Average CQI value for all DL CCs or multiple DL CCs.

(2) Multiple carrier wideband PMI: Average PMI value for all DL CCs or multiple DL CCs.

(3) Multiple carrier wideband RI (CQI): Average RI value for all DL CCs or multiple DL CCs.

(4) Carrier selective CQI (Carrier selective CQI): A CQI for one or more DL CCs selected by a terminal among a plurality of DL CCs. It may include an index (eg, CIF) or a bitmap for indicating the selected DL CC. If there are a plurality of selected DL CCs, the carrier selective CQI may be an average CQI. Alternatively, the carrier selective CQI may be represented by a best CQI value and a difference value based on the best CQI value.

(5) Carrier selective PMI (Parrier selective PMI): PMI for one or more DL CCs selected by the terminal among a plurality of DL CCs. It may include an index or a bitmap for indicating the selected DL CC. If there are a plurality of selected DL CCs, the carrier selective PMI may be an average PMI. Alternatively, the carrier selective PMI may be represented by a best PMI value and a difference value based on the best PMI value.

When reporting CQI for CoMP, the CQI may include at least one of the following. Hereinafter, multiple cells are defined by a cell list shared between a base station and a terminal.

(1) Multiple cell CQI: Average CQI for multiple cells. The average CQI may include wideband CQI and / or subband CQI.

(2) Multiple cell PMI: Average PMI for multiple cells. The average PMI may include wideband PMI and / or subband PMI.

(3) Multiple cell CQI (RI): RI for multiple cells.

(4) cell selective CQI: A CQI for one or more cells selected by a terminal among multiple cells. It may include an index or a bitmap to indicate the selected cell. If there are a plurality of selected cells, the cell selective CQI may be an average CQI. Alternatively, the cell selective CQI may be represented by a best CQI value and a difference value based on the best CQI value.

(5) cell selective PMI: PMI for one or more cells selected by a terminal among multiple cells. It may include an index or a bitmap to indicate the selected cell. When there are a plurality of selected cells, the cell selective PMI may be an average PMI. Alternatively, the cell selective PMI may be represented by a best PMI value and a difference value based on the best PMI value.

10 is a block diagram illustrating a wireless communication system in which an embodiment of the present invention is implemented.

The base station 10 includes a processor 11, a memory 12, and a radio frequency unit (RF) 13.

The processor 11 implements the proposed functions, processes and / or methods. The above-described operation of the base station 10 may be implemented by the processor 11. The processor 11 supports an operation for multiple carriers and requests a CQI. Scheduling for a carrier / cell may be performed based on the reported CQI.

The memory 12 is connected to the processor 11 to store protocols or parameters for multi-carrier operation. The RF unit 13 is connected to the processor 11 and transmits and / or receives a radio signal.

The terminal 20 includes a processor 21, a memory 22, and an RF unit 23.

The processor 21 implements the proposed functions, processes and / or methods. The above-described operation of the terminal 20 may be implemented by the processor 21. The processor 21 supports the multi-carrier operation and reports the CQI for the multi-carrier according to the CQI request.

The memory 22 is connected to the processor 21 to store protocols or parameters for multi-carrier operation. The RF unit 23 is connected to the processor 21 to transmit and / or receive a radio signal.

Processors 11 and 21 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memories 12 and 22 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media and / or other storage devices. The RF unit 13 and 23 may include a baseband circuit for processing a radio signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. Modules may be stored in memories 12 and 22 and executed by processors 11 and 21. The memories 12 and 22 may be inside or outside the processors 11 and 21, and may be connected to the processors 11 and 21 by various well-known means.

In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

The above-described embodiments include examples of various aspects. While not all possible combinations may be described to represent the various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, the invention is intended to embrace all other replacements, modifications and variations that fall within the scope of the following claims.

Claims (12)

1. In a channel state reporting method in a multi-carrier system,

   The terminal receives an uplink grant including an uplink resource allocation and a channel quality indicator (CQI) request through one downlink carrier among a plurality of downlink carriers, and

   And reporting, by the terminal, CQI for the plurality of downlink carriers over a plurality of subframes according to the CQI request.
2. The method of claim 1, wherein the CQI for each of the plurality of downlink carriers is reported in each of the plurality of subframes.
3. 3. The method of claim 2, wherein the plurality of subframes are spaced at offset intervals.
4. 4. The method of claim 3, wherein the CQI for each of the plurality of downlink carriers is reported using the uplink resource allocation in each of the plurality of subframes.
5. The method of claim 2, further comprising setting a reporting mode for reporting CQI for each of the plurality of downlink carriers.
6. The method of claim 5, wherein the reporting mode is set differently according to activation or deactivation of a downlink carrier.
7. 3. The method of claim 2, wherein an order for each of the plurality of downlink carriers for which CQI is reported is predetermined.
8. The method of claim 1, wherein the CQIs for the plurality of downlink carriers are reported on an uplink data channel configured using the uplink resource allocation.
9. The method of claim 8, wherein the uplink carrier on which the uplink data channel is transmitted is an uplink reference carrier.
10. In a terminal supporting multiple carriers,

    RF unit for transmitting and receiving a radio signal; And

    And a processor connected to the RF unit, wherein the processor

    Receiving an uplink grant including an uplink resource allocation and a CQI request through one downlink carrier of the plurality of downlink carriers, and

    A UE for reporting CQI for the plurality of downlink carriers over a plurality of subframes according to the CQI request.
11. The UE of claim 10, wherein the processor reports a CQI for each of the plurality of downlink carriers in each of the plurality of subframes.
12. The terminal of claim 11, wherein the plurality of subframes are spaced at offset intervals.

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